1. Technical Field
Methods for forming capacitors of semiconductor devices are disclosed, and more particularly, methods for forming capacitors are disclosed wherein the capacitors comprise a contact plug, a diffusion barrier film, a lower electrode formed of ruthenium (hereinafter, referred to as xe2x80x98Ruxe2x80x99), a dielectric film formed of high dielectric constant material and an upper electrode, and wherein the diffusion barrier film prevents diffusion of oxygen atoms during a deposition process and thermal treatment of the dielectric film to reduce degradation of characteristics of the device.
2. Description of the Related Art
A conventional diffusion barrier film is composed of TiN, TiAlN, TiSiN or TaSiN. A lower electrode composed of Ru or platinum is formed on the diffusion barrier film. A dielectric film is formed on the lower electrode using high dielectric constant materials such as BST or tantalum oxide film.
Here, the deposition process of dielectric film having high dielectric constant is carried out under oxygen atmosphere using a high thermal treatment method. As a result, oxygen atoms diffuse into the lower electrode and oxidize the diffusion barrier film.
In addition, when the lower electrode is composed of Ru film, molecular structure of Tris(2,4-octanedionato) ruthenium which is a source material must be broken down to allow the deposition of Ru film. Here, oxygen used as a reaction gas penetrates into the Ru film and diffuses through the lower electrode during the subsequent thermal process, thereby oxidizing a diffusion barrier film under the lower electrode. The oxidized diffusion barrier film degrades electrical characteristics of device.
Accordingly, methods for forming capacitors of semiconductor devices are disclosed wherein the capacitors comprise a diffusion barrier film having strong chemical bond, amorphous structure without rapid diffusion path of oxygen and low electrical resistance in order to prevent degradation of characteristics of device during the subsequent high temperatures thermal process.
In order to produce the above-described capacitors one disclosed method comprises:
(a) forming a diffusion barrier film, wherein the diffusion barrier film includes a RuTiN film or RuTiN/RuTiO stacked film on a contact plug for a capacitor;
(b) thermally processing the diffusion barrier film via RTP under O2 gas atmosphere; and
(c) sequentially forming a lower electrode, a dielectric film and an upper electrode on the diffusion barrier film.
It is preferable that the RuTiN/RuTiO stacked film further comprises a plurality of RuTiN/RuTiO stacked films.
It is preferable that the step of thermally processing the diffusion barrier film further comprises a step of making the surface of the diffusion barrier film dense using ionized gas.
It is preferable that the step of forming a diffusion barrier film comprises a CVD process for forming the RuTiN film having a thickness ranging from 200 to 1000 xc3x85 performed at a temperature ranging from 100 to 900xc2x0 C.
It is preferable that the RuTiN film comprises Ru ranging from about 50 to about 90 atom %, Ti ranging from about 10 to about 50 atom % and N ranging from about 1 to about 80 atom %.
It is more preferable that the RuTiN film comprises Ru ranging from about 60 to about 90 atom %, Ti ranging from about 10 to about 40 atom % and N ranging from about 5 to about 40 atom %.
It is preferable that the step of forming a diffusion barrier film comprises a CVD process for forming the RuTiO film having a thickness ranging from 200 to 1000 xc3x85 performed at a temperature ranging from 100 to 900xc2x0 C.
It is preferable that the RuTiO film of RuTiN/RuTiO stacked film comprises Ru ranging from about 50 to about 90 atom %, Ti ranging from about 10 to about 50 atom % and 0 ranging from about 1 to about 50 atom %.
It is preferable that the RuTiO film of RuTiN/RuTiO stacked film comprises Ru ranging from about 60 to about 90 atom %, Ti ranging from about 10 to about 40 atom % and O ranging from about 5 to about 40 atom %.
It is preferable that the step of forming the diffusion barrier film further comprises a purge process using a purge gas selected from the group consisting of N2, He, Ne, Ar, H2 and mixed gas thereof.
It is preferable that the step of forming the diffusion barrier film employs a Ru precursor selected from the group consisting of RuX2 and RuX3 (where, X is selected from the group consisting of H, F, Cl, Br, I, C1-C10 alkyl, C2-C10 alkenyl, C1-C8 alkoxy, C6-C12 aryl, C1-C8 alkylcyclopentadienyl, cyclopentadienyl, xcex2-diketonates, C1-C10 alkyl substituted with halogen, C2-C10 alkenyl substituted with halogen, C1-C8 alkoxy substituted with halogen, C6-C12 aryl substituted with halogen, C1-C8 alkylcyclopentadienyl substituted with halogen, cyclopentadienyl substituted with halogen and xcex2-diketonates substituted with halogen).
It is preferable that the Ru precursor comprises Bis(ethylcyclopentadienyl) ruthenium, Tris(2,4-octanedionato)ruthenium or Tris(6-methyl-2,4-heptanedionato) ruthenium.
It is preferable that the step of forming the diffusion barrier film employs a Ti precursor selected from the group consisting of TiY4 and TiY2 (where, Y is selected from the group consisting of H, F, Cl, Br, I, C1-C10 alkyl, C2-C10 alkenyl, C1-C8 alkoxy, C6-C12 aryl, C1-C8 alkylcyclopentadienyl, cyclopentadienyl, xcex2-diketonates, C1-C10 alkyl substituted with halogen, C2-C10 alkenyl substituted with halogen, C1-C8 alkoxy substituted with halogen, C6-C12 aryl substituted with halogen, C1-C8 alkylcyclopentadienyl substituted with halogen, cyclopentadienyl substituted with halogen and xcex2-diketonates substituted with halogen).
It is preferable that the Ti precursor comprises Titanium tetrachloride or Titanium tetraisopropoxide.
It is preferable that the diffusion barrier film is formed using a reaction gas selected from the group consisting of O2, NH3, H2O, H2O2, ROH, RCOOH, C2-C10 diol and mixtures thereof (where, R is selected from the group consisting of H, C1-C10 alkyl, C2-C10 alkenyl, C1-C8 alkoxy, C6-C12 aryl, C1-C10 alkyl substituted with halogen, C2-C10 alkenyl substituted with halogen, C1-C8 alkoxy substituted with halogen and C6-C12 aryl substituted with halogen).
It is preferable that the thermally processing the step (b) is performed under a gas atmosphere selected from the group consisting of O2 gas, mixture gas of Ar and O2, mixture gas of N2 and O2 and combinations thereof.
It is preferable that the step of making the surface of the diffusion barrier film dense using ionized gas comprises (i) process comprising the steps of impacting the diffusion barrier film with ionized O2, ionized Ar, ionized Ar and O2, ionized N2 and ionized N2 and O2; thermally treating the diffusion barrier film; and forming a uniform oxide layer on the surface of the diffusion barrier film using O2 ion, (ii) process comprising the steps of thermally treating the diffusion barrier film under NH3 gas atmosphere, NH3 plasma or NH3/O2 plasma atmosphere; and forming a uniform oxide layer on the surface of the diffusion barrier film using O2 ion, (iii) process comprising steps of thermally treating the diffusion barrier film using UV-O3 to form a surface layer or (iv) combinations thereof.
It is preferable that the thermally processing the diffusion barrier film is performed at a temperature ranging from 100 to 650xc2x0 C. for a time period ranging from 1 to 5 minutes.
It is preferable that the dielectric film is selected from the group consisting of a Ta2O5 film, a BST film, a PZT film, a SBT film, a BLT film and mixtures thereof.
A diffusion barrier film is formed that has an oxidation tolerance at high temperature under oxygen atmosphere, which prevents degradation of characteristic of device during the subsequent thermal process.
A diffusion barrier film is required to prevent diffusion of oxygen atoms and must be oxidation-resistant. In order to prevent diffusion of oxygen at high temperature, the diffusion barrier film has an amorphous structure because the crystallization generates grain boundary, which is a rapid diffusion path of oxygen. In addition, the diffusion barrier film must have strong chemical bonding between each constituent to prevent oxidation and maintain conductivity after reaction with oxygen.
Accordingly, a diffusion barrier film according to the present invention comprises Ru which is a quasi-precious metal, as matrix and has oxygen or nitrogen and a small amount of Ti which is a heat-resistant metal added thereto. So that the diffusion barrier film has an amorphous structure due to strong chemical bonding of oxygen or nitrogen and so that the amorphous structure is maintained even at high temperature due to Ti. Additionally, a conductive oxide film is obtained even after a reaction with oxygen due to Ru, thereby preventing degradation of electrical characteristic of device.
The reaction by which a RuTiN film and RuTiO film is formed as follows.
A RuTiN film is formed on a substrate heated at a temperature ranging from 100 to 900xc2x0 C. using RuX2 as Ru precursor, TiY4 as Ti precursor and NH3 as reaction gas, according to the first and the second reaction formulas:
RuX2xe2x80x94(NH3)xe2x86x92Ru+2HX(↑)xe2x80x83xe2x80x83first formula
TiY4xe2x80x94(NH3)xe2x86x92TiN+2HY(↑)xe2x80x83xe2x80x83second formula.
The reaction gas NH3 reacts with Ru precursor and Ti precursor according to the above reaction formulas to form Ru and TiN. As a result, a RuTiN film wherein Ru and TiN are irregularly deposited is formed. Here, HX and HY, which is strong volatile reaction products, are easily removed via a vacuum.
A RuTiO film is formed on a substrate heated at a temperature ranging from 100 to 900xc2x0 C. using RuX2 as Ru precursor, TiY4 as Ti precursor and O2 as reaction gas, according to the third and the fourth reaction formulas:
RuX2xe2x80x94(O2)xe2x86x92RuOx+2XO2(↑)xe2x80x83xe2x80x83third formula
TiY4xe2x80x94(O2)xe2x86x92TiOx+4YO2(↑)xe2x80x83xe2x80x83fourth formula
The reaction gas O2 reacts with Ru precursor and Ti precursor according to the above reaction formulas to form RuOx and TiOx. As a result, a RuTiO film wherein RuOx and TiOx are irregularly deposited is formed. Here, XO2 and YO2, which is strong volatile reaction products, are easily removed via a vacuum.
However, a RuTiN film and a RuTiO film may also be formed using other Ru precursor and Ti precursor.
A RuTiN film is formed on a substrate heated at a temperature ranging from 100 to 900xc2x0 C. using RuX3 as Ru precursor, TiY4 as Ti precursor and NH3as reaction gas, according to the fifth and the sixth reaction formulas:
RuX3xe2x80x94(NH3)xe2x86x92Ru+3HX(↑)xe2x80x83xe2x80x83fifth formula
TiY4xe2x80x94(NH3)xe2x86x92TiN+HY(↑)xe2x80x83xe2x80x83sixth formula
The reaction gas NH3reacts with Ru precursor and Ti precursor according to the above reaction formulas to form Ru and TiN. As a result, a RuTiN film wherein Ru and TiN are irregularly deposited is formed. Here, HX and HY, which is strong volatile reaction products, are easily removed via a vacuum.
A RuTiO film is formed on a substrate heated at a temperature ranging from 100 to 900xc2x0 C. using RuX3 as Ru precusor, TiY4 as Ti precursor and O2 as reaction gas, according to the seventh and the eighth reaction formulas:
RuX3xe2x80x94(O2)xe2x86x92RuOx+3XO2(↑)xe2x80x83xe2x80x83seventh formula
TiY2xe2x80x94(O2)xe2x86x92TiOx+2YO2(↑)xe2x80x83xe2x80x83eighth formula
The reaction gas O2 reacts with Ru precursor and Ti precursor according to the above reaction formulas to form RuOx and TiOx. As a result, a RuTiO film wherein RuOx and TiOx are irregularly deposited is formed. Here, XO2 and YO2, which is strong volatile reaction products, are easily removed via a vacuum.
Here, the diffusion barrier film may be a RuTiN film, a RuTiN/RuTiO stacked film or a stacked structure of a plurality of RuTiN/RuTiO stacked films.